In this verse the author has used the term yak-qalam
for the wordplay with 'paper'.
In the poetry of that time, they consider wordplay too to be a verbal
device, and they call it 'wordplay' when they use one word such that it
would have some relationship and affinity,
merely verbal, with another.... In short, there's no doubt that in such cases
sometimes this wordplay, sometimes .zil((a
, seems good, but they carried it to such lengths that in their search for
.zila(( they have no thought for elegance of meaning
[;husn-e ma((nii] or for simplicity of words.... Undoubtedly
this is to be rejected; it is a verbal device invented [nikaalii
hu))ii] by the common people [baazaarii]; literary
people [ahl-e adab] have nowhere mentioned it. When
the loafers [lau;N;De] of the city assemble, they compose
.zila(( .... These very people have, in mushairahs
and gatherings [majlis], incited the poets to such wordplay,
and drawn them in this direction. (68-69)

yak-qalam , paper, page-- all have
an affinity.... When
in the fervor of passion and mystical knowledge I showed the contemptibleness
of the charms of the world, to this day the effect of it remains in the world.
(152)

First of all consider the affinity.
The words are so meaningful that at first glance the attention is not even
drawn to them: 'pen' [qalam], 'paper' [kaa;Ga;z],
'page' [.saf;hah], 'shape, print' [naqsh].
Now look at the meaning. Usually it is said to be a picture of the lover's
heat/speed of movement. But this theme
can also be for the beloved's heat/speed of movement.... Usually it's been
said that so much heat of movement remains in the footprint that the whole
desert lies there burning. But if this is so, then there's no way to understand
the necessity of 'a burnt paper'. In reality the meaning is, the whole desert
is not burning, rather only those places are burning where the footprints
have fallen; thus the desert presents the aspect of a burning paper. When
paper burns, it doesn't burn all at once, rather here and there glowing spots
appear on it. The young Ghalib, in a ghazal from this same period, expressed
this sight with even more beauty: {64,2}.
(1989: 81) [2006:100-01]

On the idiomatic yak-qalam construction,
see {11,1}. One of the pleasures of working
with commentators is their unpredictable outbursts. (I certainly have mine!)
Nazm has an enjoyable outburst about this verse. He seems especially provoked
by the phrase yak-qalam and its ostentatious wordplay.
He goes on at length, giving hard-to-translate examples that I have omitted,
and declaiming about how vulgar and low-class it is to engage in fancy punning
and competitive word-games. This, he says, is what the loafers and common
people do, and not what the 'proper' ghazal should do. Nazm was a Lakhnavi;
if you're interested in a more detailed account of what he describes as Lucknow
street culture, see Harcourt
and Hussain; if you know Urdu well, you can go straight to the source,
Sharar.

As usual, hanuuz (on this see {3,4})
has the two senses of 'still', emphasizing long duration, and 'now', emphasizing
newness or immediacy. And what is it that the 'still' and 'now' help us to
observe? The traces of the lover's passage through the desert; or, as Faruqi
points out, the beloved's passage. In either case, merely the act of lover's
or beloved's walking through the desert was too much for the desert to bear;
it has charred, glowing embers in footprint patterns all over it. The inflammable
sandy desert, when exposed to human passion, caved in immediately and entirely,
and resembled something as frail and destroyed as a burnt, or literally (and
more graphically) 'fire-stricken', paper. In this respect, the verse evokes
the even more extreme {5,4}, in which even
a 'passing thought' of wildness/madness inadvertently burnt up the whole desert.